Can a unlocked Iphone 3 be used on Virgin Mobile?

Can a unlocked Iphone 3 be used on Virgin Mobile?

No, and for two reasons:

1.) Virgin Mobile does not allow outside phones in their system as that has always been their policy.

2.) Even if the above was false, the iPhone 3 (and iPhone 3GS and the AT&T iPhone 4, and the original iPhone) are GSM only models and are not compatible with Virgin Mobile, which is CDMA only.